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Abstract

Two backup tests are described, done for the Post Accident Heat Removal Programme. They regard studies on the consequences of contact between molten fuel and coolant. The probabilities both of the occurrence of a vapour explosion and of the stability of a fuel jet are linked to the hypothesis that quenching and mixing of molten fuel in sodium proceeds under film boiling. If it were demonstrated that the boiling regime upon contact is violent boiling, those probabilities would be drastically reduced. Therefore the boiling regime was studied more closely; in a first step with a simulant fuel, alumina. Experimental approach: 1. Water coolant In the first experiment 1200 g of A1-2O-3 were heated in a tungsten crucible as shown in Fig. 1. The crucible bottom has a hole of 12 mm diameter, and axially was the coldest point of the crucible. Thus, when it reached the melting point of alumina, 2320 K, all the alumina flowed down as a jet. The jet impinged on the water surface, at the same height as the sodium surface in Fig. 1 and solidified in the water. It formed partly, 850 g, a stalagmite on the filter bottom (an upside-down mushroom structure), and partly, 350 g, a mass of spheres, around 3 mm diameter. Between ""mushroom"" and filter bottom occurred some burn-outs, and in those places the filter got badly damaged since two of the four stainless steel gauzes melted there. These observations indicate clearly how a jet behaves in a coolant under film boiling. The only surprising result was the large amount of spherical 1-2O-3 particles. 2. Sodium coolant Subsequently a batch of 600 g of alumina was molten. Half of this mass blocked in the release tube and the other half interacted with sodium. The sodium had a mass of 4 kg, a temperature of 475 K and was under normal argon system pressure.

Additional information

Authors: SCHINS H, JRC ISPRA ESTAB. (ITALY);HOHMANN H, JRC ISPRA ESTAB. (ITALY);MAGALLON D JRC ISPRA ESTAB. (ITALY), JRC ISPRA ESTAB. (ITALY)
Bibliographic Reference: JAHRESTAGUNG KERNTECHNIK 1984, FRANKFURT (GERMANY), MAY 22-24, 1984 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 31440 ORA
Availability: Can be ordered online
Record Number: 1989122096400 / Last updated on: 1987-01-01
Category: PUBLICATION
Available languages: en